不同农业措施对玉米截形叶螨及其天敌塔六点蓟马发生的影响

为研究农业防治方法对截形叶螨及其天敌塔六点蓟马发生的影响，作者于2012年在河北涿州开展了系列研究。试验设计了玉米3个不同播期（4月25日，5月7日，5月18日）及同一播期3种不同农事措施（玉米间作南瓜，玉米自然生草及对照）进行了田间系统调查研究。结果表明，播期对截形叶螨及其天敌塔六点蓟马的发生均有显著影响，高峰期叶螨数量从高到低为4月25日（81.48头/株）＞5月7日（20.24头/株）＞5月18日（5.32头/株），塔六点蓟马数量从高到低为4月25日（4.96头/株）＞5月7日（3.20头/株）＞5月18日（2.36头/株）；不同农事措施对截形叶螨及其天敌塔六点蓟马的发生也有显著影响，高峰期叶螨数量从高到低为间作南瓜（83.20头/株）＞对照（81.48头/株）＞生草（16.6头/株），塔六点蓟马数量从高到低为间作南瓜（4.96头/株）=对照（4.96头/株）＞生草（1.62头/株）。播期越晚叶螨发生量越小，益害比越大，5月18日（0.342）＞5月7日（0.155）＞4月25日（0.076），塔六点蓟马对叶螨防控效果越好。玉米自然生草处理中截形叶螨数量显著低于南瓜间作和对照，益害比显著高于对照，但与南瓜间作处理差异不显著。

Influence of Agricultural Practice on Occurrence of Leaf Spider Mite and Its Natural Enemy in Corn Field

Field experiments were conducted to determine effects of agricultural practices on occurrence of the spider mite Tetranychus truncates Ehara and its natural enemy Scolothrips takahashii Priesener in Zhuozhou city, Hebei province in 2012. Six treatments were set up, including three sowing dates (April 25, May 7, May 18) and three cropping systems (corn-pumpkin intercropping, corn with no-weeding, and control), to investigate population dynamics of the mite and its natural enemy. Results showed that sowing dates had a significant effect on the occurrence of T. truncates and S. takahashii, the peak number of leaf mites from high to low was April 25 (81.48 heads/plant) >May 7 (20.24 heads/plant)>May 18 (5.32 heads/plant), and the population size of S. takahashii was ranked as April 25 (4.96 heads/plant)>May 7 (3.20 heads/plant)>May 18 (2.36 heads/plant). Cropping system also had significant effects on the occurrence of T. truncates and S. takahashii, the peak number of leaf mites from high to low was corn-pumpkin intercropping (83.20 heads/plant) >CK (81.48 heads/plant) >corn with no-weeding (16.60 heads/plant), and that of S. takahashii was corn-pumpkin intercropping (4.96 heads/plant)=CK (4.96 heads/plant) >corn with no-weeding (1.62 heads/plant). Late sowing harbored higher ratio of natural enemy to the leaf mite, and thus conferred better control of the spider mite. Compared among the three cropping systems, the treatment with weeds left had higher ratio of natural enemy to pest and also showed a better control of the spider mite.